SUNRPC/cache: Fix unsafe traverse caused double-free in cache_purge (43e33924) · Commits · 戴 / test

Deleting list entry within hlist_for_each_entry_safe is not safe unless next pointer (tmp) is protected too. It's not, because once hash_lock is released, cache_clean may delete the entry that tmp points to. Then cache_purge can walk to a deleted entry and tries to double free it. Fix this bug by holding only the deleted entry's reference. Suggested-by:

NeilBrown <neilb@suse.de> Signed-off-by:

Yihao Wu <wuyihao@linux.alibaba.com> Reviewed-by:

NeilBrown <neilb@suse.de> [ cel: removed unused variable ] Signed-off-by:

Chuck Lever <chuck.lever@oracle.com>

net/sunrpc/cache.c

+3 −2

Original line number	Diff line number	Diff line
		@@ -529,7 +529,6 @@ void cache_purge(struct cache_detail *detail)
		{
		struct cache_head *ch = NULL;
		struct hlist_head *head = NULL;
		struct hlist_node *tmp = NULL;
		int i = 0;

		spin_lock(&detail->hash_lock);
		@@ -541,7 +540,9 @@ void cache_purge(struct cache_detail *detail)
		dprintk("RPC: %d entries in %s cache\n", detail->entries, detail->name);
		for (i = 0; i < detail->hash_size; i++) {
		head = &detail->hash_table[i];
		hlist_for_each_entry_safe(ch, tmp, head, cache_list) {
		while (!hlist_empty(head)) {
		ch = hlist_entry(head->first, struct cache_head,
		cache_list);
		sunrpc_begin_cache_remove_entry(ch, detail);
		spin_unlock(&detail->hash_lock);
		sunrpc_end_cache_remove_entry(ch, detail);

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